I'll be putting new shocks in the Fastback in the near future. Do coilovers offer a big improvement in handling? Can you put them on a lowered vehicle? Thanks.

I am considering fitting coilovers instead of std shocks to my fasty. Is there a discernible improvement in handling performance?

IMO, don't do it. Bad shocks. Put on a set of quality shocks like Bilstein, Koni, KYB or Boge.